Process For the Recovery of Sterols From Organic Material

ABSTRACT

A process for recovering sterols from organic material containing sterols and sterol derivatives. In a first step (a) the organic material is reacted with at least one of polyols, polyamines, alkanolamines or monohydric alcohols to increase the amount of free sterols in the organic material; (b) reacting residual reactants, and their esters or amides with epoxydated components; and (c) separating the free sterols from the mixture by short path distillation, thin film evaporation, or flash evaporation. The recovered sterols can be further purified by a crystallization step.

OBJECT OF THE INVENTION

The present invention generally belongs to the area of chemicalprocesses of isolating and purifying constituents from natural sourcesand, in particular, it relates to a new method for separatingconcentrating and purifying sterols from organic material.

STATE OF THE ART

Numerous methods have been described for the recovery of sterols fromorganic material converting sterol fatty esters into free sterols withsub-sequent purification by distillation and crystallization.

The separation of sterols by transesterification and saponificationsteps followed by further esterification or solvent extraction oftenrequires organic solvents, results to large amounts of salts as wasteand usually needs many process steps, so that the process is lesseconomic and less environmentally friendly and results in relatively lowyields.

The U.S. Pat. No. 6,344,573 B1 relates to a process for the extractionand concentration of unsaponifiables substances from residues of animalor vegetable products. This process does not require organic solventsbut involves several process steps creating a high amount ofby-products.

The European patent application EP 1291355 A1 discloses a process forrecovering sterols and/or wax alcohols from a crude tall oil materialcontaining sterols and/or wax alcohols in esterified form and fattyand/or rosin acids and optionally sterols and/or wax alcohols in freeform. Said method is comprising the steps of: converting free acids inthe source material to corresponding salts, removing water if present,transesterifying the esterified sterols and/or wax alcohols present inthe dry material obtained in step a or step b to liberate sterols and/orwax alcohols, evaporative fractionating the trans-esterified material,and isolating sterols and/or wax alcohols from the obtained fractions orthe residue.

After liberating the bonded sterols, the material is submitted to afractionation step to separate the sterols from the other components.Sterols remain in the residue stream and light end components aredistilled off. This process consists of a large number of differentsteps bearing the risk to decrease the final yield of free sterols.

A high efficiency continuous process for recovering high purity sterolmixtures from organic material including tall oil pitch is described inthe European patent application EP 1081156 A2 comprising the steps ofdistillation, crystallization and recirculation of the mother liquorresidue. In order to achieve the high purity many production steps andthe use of organic solvents was necessary.

The International application WO 00/64921 discloses a process to purifysterols from natural sources by complexation with a metal salt, thisprocess has less process steps, but requires a large amount of solvents.

Sterol concentrate purification, such as the evaporative fractionationdisclosed in the European patent application EP 1 389 622 A2 does avoidsalts and organic impurities, but again includes many process steps. TheEuropean patent EP 0 260 243 B1 describes a method to set free sterolfrom organic materials by treating said material with ammonia or aminesin order to avoid the addition of inorganic salts which complicatesfurther purification steps.

It has been an object of the present invention to provide an efficienteconomical, environmentally friendly process which provides a highprocess yield in the recovery of sterols and a high final sterol purity.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a process for the recovery of sterolsfrom organic material, which comprises

a) reacting organic material containing free sterols and sterolderivatives with

(i) polyols or

(ii) polyamines or

(iii) alkanolamines or

(iv) alcohols

to convert the sterol derivatives into free sterolsb) reacting the residual reactants and their esters or amides withepoxydated substances and subsequentlyc) separating the free sterols from the remaining components bydistillation.

As used herein the term “sterols” refers to any plant or animal basedsterol or sterol derivative for example cholesterol, sitosterol,campesterol, ergosterol, stigmasterol, brassicasterol, avenasterol aswell as the saturated components called stanols like sitostanol,stigmastanol and campestanol and their derivatives.

In nature sterols can occur as free sterols or predominantly derivatizedas sterol esters of long-chain fatty acids. During processing which isusually conducted at higher temperatures, low pressure, and relativelylong residence time, most of the sterols in organic material are furtherderivatized.

Since sterol derivatives are difficult to separate or even purify eithervia distillation, extraction or direct crystallization it is necessaryto convert them back to free sterols before proceeding with furtherprocessing steps. This high number of process steps renders a processuneconomical, so that one object of the current invention is thereduction of process steps. The enrichment of free sterols from naturalorganic material is achieved by step a) of the proposed process. Bondedsterols are converted back into free sterols using an appropriatereactant which combines a high transesterification or transamidationreaction yield with the conversion of fatty and other organic acids intotheir respective mono-, di- and polyesters, aminoamides, diamides, andpolyaminoamides. Some reactants do neither require a catalyst, reactantexcess nor high pressure to achieve complete transesterification ortransamidation, in addition no solvent is used.

In order to prevent that the low molecular weight products formed orreactants left after transesterification or transamidation such as longchain alcohols and polyalcohols, glycols and polyglycols, amines andpolyamines, alkanolamines, monoesters of polyalcohols, or amidoamineswill distill off together with the free sterols and contaminate thefinal product, the molecular weight of the non-free-sterol-material isincreased. The crucial step of the process is therefore the reaction ofthe residual reactants and their respective alkanol esters oralkanolaminoamides left after step a) with epoxydated substances. Thehigher molecular weight of the residuants after reacting with theepoxyde groups results in a decreased vapor pressure, so thatdistillative separation of free sterols from the residuants is improved.This will avoid contamination with light end materials and increase thesterol concentration in the distillate. Free sterols can now easily beseparated using a distillation apparatus with almost no theoreticalseparation stages such as molecular distillation, short pathdistillation or thin film evaporators. This process provides adistillate with a sufficient sterol concentration to produce sterolswith a purity of more than 98% using only one single crystallizationstep.

Less reaction steps and a single distillation reduce processing costssignificantly.

The organic material (feed) used in step a) can be any materialcontaining free sterols or sterol esters or other sterol derivatives,such as vegetable oil distillates (VOD) and/or deodorizer distillates(DOD), residues of fatty acids (FAR) and/or fatty acid methyl or ethylester production (FAMER, FAEER), soap stock fatty acid residues (SSFAR),sugar cane wax (SCW), crude tall oil (CTO) and tall oil pitch (TOP). Dueto its availability and amount of sterols or sterol derivatives thepreferred feed is tall oil pitch.

Deodorizer distillate (DOD) or Vegetable Oil Distillate (VOD) from thedeodorization process of vegetable oils, usually contain 2-15 wt % ofsterols, using this type of feed concentrations of up to 45 wt % of freesterols based on the weight of the concentrate can be produced.

Residues from distillation of either fatty acids (FAR) or methyl esters(FAMER) contain 2-30 wt % of sterols and can also be concentrated up to45 wt % free sterols based on the weight of the concentrate by thecurrent technique, as well as crude tall oil (CTO) from the sulphatationemployed in cellulose manufacturing, which contains 3-7 wt % sterol ortall oil pitch (TOP) derived from the process of paper production fromwood which usually has 8-16 wt % sterols. Even other organic materialssuch as sugar cane waxes (SCW) and soap stock fatty acids (SSFA) with asterol concentration below 5 wt % can be concentrated up to 45 wt %sterols based on the weight of the concentrate using the said process.Surprisingly it was found that the inventive process is always resultingin a high concentration of free sterols even if the organic material ofstep a) contains lower amounts of sterols. It is an important advantagethat the yield of sterols from this process is independent from theorganic material resp. the sterol concentration of the feed.

In step a) of the inventive process this organic material is reactedwith long chain alcohols or polyalcohols, glycols or polyglycols, aminesor polyamines, or alkanolamines and sterol esters and other sterolderivatives are transformed into the free sterols while other reactantsresult in the correspondent derivatives such as alkanol esters oramides.

Examples for polyols that could be used are

-   -   (i) polyols such as ethylene, diethylene glycol, triethylene,        tetraethylene, and polyethylene glycols with molecular weights        up to 1000, propylene glycol and polypropylene glycol having        molecular weights up to 1000, glycerine and polyglycerines, mono        and di-pentaerythritol, trimethylol-propane, high molecular        weight polyols such as C7 to C24 fatty alcohols.        Suitable polyamines are    -   (ii) ethylenediamine, triethylenetetramine, tetraethyleneamine        or dimethylpropilamines.        Alkanolamines for step a) could be    -   (iii) monoethanolamine, diethanolamine, triethalonamine,        aminoethylethanolamine, dimethylaminopropylamine.        The alcohols for this process step are    -   (iv) either from an Oxo process or linear alcohols from natural        sources including the Guebert alcohols with C6 to C36 carbon        atoms.

The preferred reactants are polyamines, most preferred isethylendiamine. The use of ethylendiamine enables the reaction withoutthe use of a catalyst, avoiding solvents and high pressure.

The amount of the reactants has to be adapted concerning thesaponification value of the used feed. The molar ratio of reactant ((i)to (iv)) in the transesterification and/or transamidation step (a) inrelation to the saponification number of the organic material (feed) is0.5 to 6.

The transesterification or transamidation is run in the presence ofmetallic catalysts, preferred are zinc oxide, sodium-, potassium- orlithium hydroxide and organic tin catalysts. Some reactants—such asalkanolamines, especially diethanolamine, do not require the use of acatalyst.

Step a) and b) can be conducted in form of a batch process (examples1-5) or in form of a continuous reaction process (examples 6, 7).

The batch process is conducted at temperatures of 150 to 290° C.,preferably 180 to 270° C., the best yield and purity is achieved attemperatures of 210 to 260° C.

The continuous reaction process starts at ambient temperature of 20 to30° C. and the temperature is increased up to 240 to 330° C., preferably250 to 310° C. and most preferred up to 270 to 300° C., while thepressure increases up to 1 to 25 bar, preferably 3 to 10 bar.

Step a) is followed by a quick reaction of the residual reactants andtheir respective alkanol esters or alkanolaminoamides left in thereaction product with the epoxy groups of the epoxydated substances.

Generally all materials with epoxy groups can be used for this reaction,preferred are epoxydated vegetable oils such as epoxydated soy bean oil(ESO), epoxydated linseed oil (ELO), epoxydated sunflower oil orepoxydated lard oil or epoxydated fatty acids and epoxydated fatty acidesters such as tall oil fatty acids, oleic and linoleic acids. Mostpreferred are epoxydated soy bean oil (ESO) and/or epoxydated linseedoil (ELO).

In order to achieve the best results an amount of 2 to 20 wt %epoxydated vegetable oils preferably 5 to 10 wt % based on the amount ofthe feed used in step a) is added.

The temperature for the reaction of step b) is 120 to 220° C.,preferably 150° to 200° C., especially 170° C. to 190° C. if the processis conducted as a batch process. In case of a continuous process thehigh temperature during step a) is rapidly cooled down after addition ofthe epoxydated material.

Without addition of the epoxydated substances the overall yield of freesterols is only 30 wt % while with step b) a free sterol yield of 40 to45 wt % based on the weight of the concentrate can be achieved.

The result of a Gel Permeation Chromatography (GPC) in FIG. 1 shows theprocess principle and the typical molecular weight growing profile froma typical feed during the transesterification or transamidation process,and after adding the epoxydated material.

(Line 1 represents the organic material (feed), line 2 the reactionproduct after 2 h reaction, line 3 is the reaction product 0.5 h afteraddition of ESO and line 4 represents the reaction product 1 h afteraddition of ESO).

Free sterols can then easily be separated using single distillationapparatus such as short path or thin film evaporation equipment, flashevaporators or molecular distillation. The possibility to use preferablyshort path distillation or molecular distillation enables the use of lowdistillation temperatures and low vacuum to avoid degradation and lossof sterols. The high reaction yield after step b) combined with a shortpath distillation results in a very short residence time avoidingsterols degradation or any other side reactions such as sterol esterformation and results in a process yield of more than 95% based on thetotal amount of sterols.

Most preferred is a short path destillation, which is operated at areduced pressure of 0.01 to 10 mm/Hg and a temperature of 180 to 310° C.and/or a fractionation column which is operated at 0.1 to 5 mmHg and atemperature of 170 to 230° C. at the top and 240 to 280° C. at thebottom.

After concentration of the sterols a final crystallisation process canbe added as step d) in order to purify the sterols. Preferably thiscrystallisation does just include one crystallisation cycle. A sterolpurification of 98 wt % and higher can be reached in just one singlecrystallisation step using the concentrated sterols resulting from stepa to c).

EXAMPLES

The examples describe the use of polyalcohols, long chain alcohols,polyamines and alkanolamines as reactants to set the sterols free bytrans-esterification or transamidation of vegetable oil distillate(VOD), crude tall oil (CTO), tall oil pitch (TOP), fatty acid methylester residues (FAMER), sugar cane wax (SCW). After releasing thesterols and reaction of the residual reactants and their esters oramides with epoxydated products this material is distilled at hightemperature and low pressure in order to separate the free sterols fromthe other high boiling point components.

Step a)—Transesterification and/or Transamidation Step and Step b)

Example 1

1 kg of TOP were reacted with 155 g (2.53 moles) monoethanolamine fromAldrich Chemical Co. and 10 g zinc oxide (0.12 moles) from Merck KGaA,in a 2-liter, 3-necked round bottom flask equipped with a thermometerand mechanical agitator at a temperature of 220° C. for 5 h. Then 50 gof epoxydated soy bean oil (ESO) were added to the flask, reactiontemperature was maintained at 180° C. and the reaction was continued for1 hour. The yield of sterol release—relation of free sterols in thereaction product after step a and b compared to the total amount of freeand derivatized sterols in the feed—was 99.34%.

Example 2

1 kg of VOD was treated with 326 g (3.1 moles) of diethyleneglycol fromAldrich Chemical Co. and 17 g of zinc oxide (0.21 moles) from MerckKGaA, in a 2-liter, 3-necked round bottom flask equipped with athermometer and mechanical agitator at a temperature of 220° C. After 5hours 80 g of ESO were added to the flask, reaction temperature wasmaintained at 180° C. and the reaction was continued for 1 hour. Theyield of sterol release was 90.74%.

Example 3

1 kg of TOP was reacted with 60 g (1.00 moles) of ethylenediamine fromAldrich Chemical Co. into a 2-liter, 3-necked round bottom flaskequipped with a thermometer and mechanical agitator at a temperature of220° C. for 3 h. After reaction completion 70 g of ESO were added to theflask, reaction temperature was maintained at 180° C. and the reactionwas continued for 1 hour. The yield of sterol liberation was 99.7%.

Example 4

1 kg of FAMER was reacted with 470 g (5.11 moles) of Glycerol fromAldrich Chemical Co. and 1.7 g of Lithium Hydroxide (1.0 mol) from MerckKGaA, in a 2-liter, 3-necked round bottom flask equipped with athermometer and mechanical agitator at a temperature of 240° C. After 5h 60 g of ESO were added to the flask, reaction temperature wasmaintained at 180° C. and the reaction was continued for 1 hour. Theyield of sterol liberation was 85%.

Example 5

1 kg of VOD was reacted with 90 g of ethylenediamine (1.5 moles)obtained from Aldrich Chemical Co., in a 2-liter, 3-necked round bottomflask equipped with a thermometer and mechanical agitator at atemperature of 220° C. After 4 hours 90 g of ESO were added to theflask, reaction temperature was maintained at 180° C. and the reactionwas continued for 1 hour. The yield of sterol release was 99.5%.

Example 6

0.9 kg of TOP were mixed with 60 g of ethylenediamine (1.0 moles)obtained from Aldrich Chemical Co., and transferred into a pressurereactor. Within 20 minutes temperature was increased from initially 25°C. to 290° C. and maintained for another 20 minutes, a maximum pressureof 6 bar was achieved. The pressure was released to atmospheric pressureand 60 g of ESO were added, the temperature was kept for another 5minutes and then cooled down to ambient temperature (25° C.) within 25minutes. The yield of sterol release was 98.0%.

Example 7

0.9 kg of TOP were mixed together with 60 g of ethylenediamine (1.0moles) obtained from Aldrich Chemical Co., and transferred into apressure reactor. Within 20 minutes temperature was increased frominitially 25° C. to 275° C. and maintained for another 20 minutes, amaximum pressure of 4 bar was achieved. The pressure was released toatmospheric pressure and 60 g of ESO were added, the temperature waskept for another 5 minutes and then cooled down to ambient temperature(25° C.) within 25 minutes. The yield of sterol release was 95.0%.

Step c)—Concentrating the Sterols using Short Path Distillation:

Example 8

1 kg of the product from example 1 was distilled off in a short pathevaporator (SPE) which was operated at 0.1 mm Hg, 290° C. and a feedflow of 600 ml/hour. The residue 1 leaving the bottom of the SPErepresented 55% w/w of the CTO feed. The top fraction 2 was representing45% w/w with 24% of free sterols. The sterols recover yield in thisstep—amount of concentrated free sterols after distillation compared toamount of free sterols from steps a and b used for distillation—was 83%.

Example 9

1 kg of the product from example 3 was distilled off in a SPE which wasoperated at 0.1 mm Hg, 290° C. and a feed flow of 600 ml/hour. Theresidue 1 leaving the bottom of the WFE represented 67% w/w of the feed.The top fraction 2 was representing 33% w/w with 40% of free sterols.The sterols recover yield in this step was 97.1%.

This sterols have further been purified by a one step crystallization:

80 g of the crude sterols were dissolved in 184 g of n-heptane at 65° C.in a jacketed glass reactor of 1000 ml with a diameter of 105 mmequipped with a KPG-stirrer (plate stirrer) and a reflux cooler. Afterachieving a clear solution 16 g of methanol/DI-water (50/50 wt %) wasadded. Crystallization of sterols started immediately. The slurry wasfurther cooled down to a product temperature of 25° C. in 40 minutes.The crystallized slurry was filtered using the Buchner vacuum funnel tofiltrate off the mother liquor. The residual cake was washed two timeswith 100 ml of fresh n-heptane at ambient temperature. The final sterolpotency was 98.2%.

Example 10

1 kg of the product from example 2 was distilled off in a SPE which wasoperated at 0.1 mm Hg, 290° C. and a feed flow of 600 ml/hour. Theresidue 1 leaving the bottom of the WFE represented 73.4% w/w of thefeed. The top fraction 2 was representing 26.6% w/w with 28.6% of freesterols. The sterols recover yield in this step was 73%.

Example 11

0.9 kg of the product from example 6 was distilled off in a SPE whichwas operated at 0.1 mm Hg, 280° C. and a feed flow of 600 ml/hour. Theresidue 1 leaving the bottom of the WFE represented 67% w/w of the feed.The top fraction 2 was representing 33% w/w with 38% of free sterols.The sterols recover yield in this step was 94.8%.

These sterols have further been purified by a one step crystallization:

80 g of the crude sterols were dissolved in 192 g of n-hexane at 65° C.in a jacketed glass reactor of 1000 ml with a diameter of 105 mmequipped with a KPG-stirrer (plate stirrer) and a reflux cooler. Afterachieving a clear solution 8 g of methanol/DI-water (50/50 wt %) wasadded. Crystallization of sterols started immediately. The slurry wasfurther cooled down to a product temperature of 25° C. in 40 minutes.The crystallized slurry was filtered using the Buchner vacuum funnel tofiltrate off the mother liquor. The residual cake was washed two timeswith 100 ml of fresh n-hexane at ambient temperature. The final sterolpurity was 98.5%.

1-13. (canceled)
 14. A process for the recovery of sterols from steroland sterol derivative containing organic feed material, which comprises:a) reacting the organic feed material containing free sterols and sterolderivatives with at least one member selected from the group consistingof polyols, polyamines, alkanolamines and alcohols to convert the sterolderivatives to free sterols, to provide a mixture containing freesterols and residual components; b) reacting the residual components andtheir esters or amides with an epoxydated component to provide anepoxylated mixture; and c) separating the free sterols from theepoxylated mixture by distillation.
 15. The process according to claim14, wherein, the sterol containing organic material comprises at leastone member selected from the group consisting of vegetable oildistillates, deodorizer distillates, residues of fatty acid production,residues of fatty acid ester production, soap stock fatty acid residues,sugar cane wax, crude tall oil and tall oil pitch.
 16. The processaccording to claim 14, wherein, the epoxydated components used in stepb) comprises at least one member selected from the group consisting ofepoxydated soy bean oil, epoxydated linseed oil, epoxydated sunfloweroil, epoxydated lard oil, epoxydated fatty acids and epoxydated fattyacid esters.
 17. The process according to claim 14, wherein, in step b,the epoxydated component is added in an amount of 2 to 20 wt % based ona weight of organic material feed in step a).
 18. The process accordingto claim 14, wherein, step a) is carried out in the presence of a metalbased catalyst.
 19. The process according to claim 14, wherein, step a)is carried out without addition of a catalyst.
 20. The process accordingto claim 14, wherein, steps a) and b) are conducted as a batch processor as a continuous process.
 21. the process according to claim 14,wherein, transesterification and/or transamidation of step a) isconducted at a temperature of 150° C. to 290° C. in a batch process. 22.The process according to claim 14, wherein, the transesterificationand/or transamidation of step a) is conducted at increasing temperaturesup to 240° C. to 330° C. in a continuous process.
 23. The processaccording to claim 14, wherein, step b) is conducted at a temperature of120° C. to 220° C.
 24. The process according to claim 14, wherein, themolar ratio of the at least one member in step (a) in relation to asaponification number of the organic feed material is 0.5 to
 6. 25. Theprocess according to claim 14, wherein, step c) is conducted by at leastone process selected from the group consisting of short pathdistillation, thin film evaporation, flash evaporation and moleculardistillation.
 26. The process according to claim 14 further comprising acrystallisation step (d) carried out after step c) for furtherpurification of the separated sterols.
 27. The process according toclaim 16, wherein, the epoxydated component comprises at least a memberselected from the group consisting of epoxydated tall oil fatty acids,oleic acid and linoleic acid and epoxydated tall oil fatty acid esters,oleic acid esters and linoleic acid esters.
 28. The process of claim 18,wherein, the catalyst comprises at least one member selected from thegroup consisting of organotin catalysts, zinc oxide, sodium hydroxide,potassium hydroxide and lithium hydroxide.